Avalanche Forecast

Issued: Apr 16th, 2017 8:00AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs, Cornices and Loose Wet.

chris gooliaff, Parks Canada

Glacier.

Touchy wind slabs in the alpine are sensitive to human triggering. Down in the valley, daytime warming and sunshine will break down the surface crust and raise the danger level.

Summary

Weather Forecast

Cloudy with sunny periods today, with light W alpine winds and freezing levels rising to 1900m. Monday will see much of the same with some isolated flurries resulting from the unstable air mass over BC.

Snowpack Summary

10-15cm of new snow at treeline. Settling storm snow in the top 60cm overlies a series of crusts on most aspects up to 1900m. Moderate SW winds at tree-line and alpine have formed wind slabs on lee features. Cold, dry snow can be found on northerly slopes while solar aspects rapidly become moist with sunshine. Huge cornices line the upper ridges.

Avalanche Summary

A field team encountered touchy surface wind slabs in northerly lee aspects at 2200m yesterday. The 10-15cm soft slabs were easily failing with ski cuts and running fast on a temp crust. On Friday, several large avalanches from Mt Macdonald to size 3.5 were observed running to the valley floor, likely cornice triggered.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

Wind Slabs

Touchy surface slabs are sensitive to human triggering in wind-exposed alpine and tree-line areas. These sit on sun or temp crusts, depending on the aspect, up to at least 2200m.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use caution in lee areas. Recent wind loading have created wind slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

The cornices are as big as they are going to get. Predicting their failure is tricky, but daytime warming or direct sun will weaken them. They have triggered some very large natural avalanches in and near Rogers Pass recently.

Stay well to the windward side of corniced ridges.Minimize exposure to overhead hazard from cornices.

Aspects: North, North East, East, South East, South.

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 4

Loose Wet

Southerly aspects below tree-line have the potential to spit out loose wet avalanches if freezing levels rise to 1900m and we receive the forecasted sunshine. The morning surface crust will break down rapidly if these 2 things happen.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 17th, 2017 8:00AM